1. Field of the Invention
The present invention relates to the field of medical devices. More particularly, the present invention relates to the field of fixation devices for compressing bone fractures of a human being.
2. Description of the Prior Art
U.S. Pat. No. 5,693,055 by the same inventors discloses a unique odd angle internal fixation device for a transverse fracture located at the junction of the metaphysis and diaphysis of a long bone such as the proximal humerus. The device includes an elongated lag screw and a rectangular shaped guide plate. The lag screw is introduced through the diaphyseal segment of the fracture at an angle ranging approximately between 155° to 170°, cross fixing the bone fracture line and settling in the depth of the epiphysis. The guide plate serves as a guide for the lag screw and allows the engagement of the head of the lag screw to the inner wall of its short barrel portion. The engagement causes the guide plate which is attached to the barrel to be compressed against the diaphyseal cortex as the lag screw advances deeper into the epiphysis at an angle ranging approximately between 155 degrees to 170 degrees. The device provided with a lag screw and a guide plate which has an inclined short barrel portion integrally attached to the guide plate at an angle from above said range will cross fix a fracture line of the junction of the metaphysis and diaphysis, or cross fix the osteotomy site of the junction of the metaphysis and diaphysis or it can be used for joint fusion.
It will be appreciated that the U.S. Patent discloses the device which has a correct mechanism for fixing the bone transverse fracture. However it must also be appreciated that there are a number of areas where the structure of the device could be improved so as to fix both longitudinal and transverse fractures.
This prior art odd angle internal bone fixation device with the screw having a slotted top end from its proximal head does not create a user friendly condition for a surgeon. This is because surgeon can only tighten the lag screw when the position of the flat head of a screw driver used by the surgeon matches the position of the slotted top end of the lag screw. Therefore, the surgeon must redirect part of his attention to the position of the screw driver he is using, which could create problems if the surgeon must divert his attention from the medical issues of the surgical operation.
In addition, this prior art rectangular shaped guide plate of the device also does not create a user friendly condition for the surgeon since it is difficult for the surgeon to stabilize the plate at a position of the diaphsis cortex of the humerus determined by the surgeon, and in addition the plate is unstable in operation when the lag screw is pushed and turned to settle into the bone. An appropriate structural fixture designed for the plate is necessary to make it easily lock at a position of the diaphsis cortex and further keep it stable during operation when the lag screw is pushed and turned into the bone structure.
Another problem with the prior art device is that the screw which settles in the depth of the epiphysis after surgery could be loosened from its initial position if a patient performs excess movement of the body part where the fractured bone is located. To avoid such risk, the patient is advised to have a limited movement of the body part until the screw is fussed with the born structure, which could take a long time to happen. Obviously, this creates potential problems for the patient.
In addition, it is difficult for the surgeon to precisely follow a desired angle for driving the lag screw to settle into the bone without having a guide hole with the desired angle through a path that the lag screw is intended to drive through.
There is a significant need for a device which can be used to fix a longitudinal bone fracture in addition to its application to fix a transverse bone fracture, since longitudinal bone fractures also frequently occur.